The present invention relates to a closing unit for an injection molding machine with a stack mold.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
A closing unit of a type involved here includes two platens and an intermediate plate, also called stack platen, which is disposed between the two platens, with a molding tool being provided between one platen and the intermediate plate and another molding tool disposed between the other platen and the intermediate plate, so as operate for stack application. In this way, several molding tools with at least two mold cavities can be provided and maintained in a closed state by applying a same clamping force. When the intermediate plate is constructed as a swivel (or rotary) platen, a product can be produced in a first cavity, and after rotation of the swivel platen, a further normally different material can be applied onto the product in a second cavity to produce a finished multi-component product, such as, e.g. two-component or three-component products. The intermediate plate is able to rotate and may also be constructed for linear movement in opening and closing directions. Examples of stack molds with swivel platen construction are disclosed in German Offenlegungsschrift DE 101 52 394, European Pat. Publ. No. EP 0 895 848, and European Pat. No. EP 1 119 449.
These conventional injection molding machines with a closing unit of a type described above are suitable for an operator only in those situations when both mold cavities are utilized for making the product. A closing unit with an intermediate plate is, however, unsuitable for use as a single-face mold for making a single-component product.
It would therefore be desirable and advantageous to provide an improved closing unit to obviate prior art shortcomings and to enhance versatility by allowing its application as a single-face mold as well as for producing multi-component products.